Simplify and fix urllib.parse.urlencode() (#13815)

Remove overloads and type vars. Introduce a protocol for the
`quote_via` argument. This means that the interface accepted by the
supplied `quote_via` is stricter, and is not dependent on the actual
supplied types in the `query` argument, but must work with all
possible query types.

Author: srittau

stdlib/@tests/test_cases/urllib/check_parse.py

@@ -0,0 +1,12 @@
+from __future__ import annotations
+
+from urllib.parse import quote, quote_plus, urlencode
+
+urlencode({"a": "b"}, quote_via=quote)
+urlencode({b"a": b"b"}, quote_via=quote)
+urlencode({"a": b"b"}, quote_via=quote)
+urlencode({b"a": "b"}, quote_via=quote)
+mixed_dict: dict[str | bytes, str | bytes] = {}
+urlencode(mixed_dict, quote_via=quote)
+
+urlencode({"a": "b"}, quote_via=quote_plus)

stdlib/urllib/parse.pyi

@@ -1,7 +1,7 @@
 import sys
-from collections.abc import Callable, Iterable, Mapping, Sequence
+from collections.abc import Iterable, Mapping, Sequence
 from types import GenericAlias
-from typing import Any, AnyStr, Generic, Literal, NamedTuple, TypeVar, overload
+from typing import Any, AnyStr, Generic, Literal, NamedTuple, Protocol, overload, type_check_only
 from typing_extensions import TypeAlias
 
 __all__ = [
@@ -132,38 +132,32 @@ def urldefrag(url: str) -> DefragResult: ...
 @overload
 def urldefrag(url: bytes | bytearray | None) -> DefragResultBytes: ...
 
-_Q = TypeVar("_Q", bound=str | Iterable[int])
+# The values are passed through `str()` (unless they are bytes), so anything is valid.
 _QueryType: TypeAlias = (
-    Mapping[Any, Any] | Mapping[Any, Sequence[Any]] | Sequence[tuple[Any, Any]] | Sequence[tuple[Any, Sequence[Any]]]
+    Mapping[str, object]
+    | Mapping[bytes, object]
+    | Mapping[str | bytes, object]
+    | Mapping[str, Sequence[object]]
+    | Mapping[bytes, Sequence[object]]
+    | Mapping[str | bytes, Sequence[object]]
+    | Sequence[tuple[str | bytes, object]]
+    | Sequence[tuple[str | bytes, Sequence[object]]]
 )
 
-@overload
-def urlencode(
-    query: _QueryType,
-    doseq: bool = False,
-    safe: str = "",
-    encoding: str | None = None,
-    errors: str | None = None,
-    quote_via: Callable[[AnyStr, str, str, str], str] = ...,
-) -> str: ...
-@overload
-def urlencode(
-    query: _QueryType,
-    doseq: bool,
-    safe: _Q,
-    encoding: str | None = None,
-    errors: str | None = None,
-    quote_via: Callable[[AnyStr, _Q, str, str], str] = ...,
-) -> str: ...
-@overload
+@type_check_only
+class _QuoteVia(Protocol):
+    @overload
+    def __call__(self, string: str, safe: str | bytes, encoding: str, errors: str, /) -> str: ...
+    @overload
+    def __call__(self, string: bytes, safe: str | bytes, /) -> str: ...
+
 def urlencode(
     query: _QueryType,
     doseq: bool = False,
-    *,
-    safe: _Q,
+    safe: str | bytes = "",
     encoding: str | None = None,
     errors: str | None = None,
-    quote_via: Callable[[AnyStr, _Q, str, str], str] = ...,
+    quote_via: _QuoteVia = ...,
 ) -> str: ...
 def urljoin(base: AnyStr, url: AnyStr | None, allow_fragments: bool = True) -> AnyStr: ...
 @overload